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March 2011
EVAR for Ruptured Abdominal Aortic Aneurysms
Tips for improving survival rates among patients who undergo endovascular repair of rAAAs.
By Frank J. Veith, MD; Neal S. Cayne, MD; Todd L. Berland, MD; Dieter Mayer, MD; and Mario Lachat, MD
Ruptured abdominal aortic aneurysms (rAAAs) are being treated by endovascular aneurysm repair (EVAR) and other endovascular techniques with increasing frequency. Endovascular procedures offer many potential advantages over open repair (OR); they are less invasive, eliminate damage to periaortic and abdominal structures, decrease bleeding from surgical dissection, minimize hypothermia, and lessen the requirement for deep anesthesia.
Because of these advantages, EVAR has been used extensively to treat rAAAs by several groups who have achieved good results.1-8 In contrast, some other groups have been unable to demonstrate the superiority of EVAR over OR in the rAAA setting.9,10 This article describes some of the strategies, techniques, and adjuncts that facilitate the endovascular treatment of rAAAs. We believe that these all contribute to improved outcomes in terms of enhanced survival rates in a group of patients that is difficult to treat.
STRATEGIES, TECHNIQUES, AND ADJUNCTS
Standard Approach and Protocol
Having a standard approach and protocol promotes
effective decision making and treatment for patients in confusing
and stressful circumstances.6,7 They are also important
in facilitating education in and recognition of rAAAs by
generalists, emergency department personnel, and others to
enable early diagnosis and mobilization of the specialized
caregivers who are best trained to optimize treatment.
Fluid Restriction
Fluid resuscitation (hypotensive hemostasis) should be
restricted even if the patient becomes hypotensive.
Experience has shown that systolic arterial pressures of
50 to 70 mm Hg are well tolerated for short periods and
limit internal bleeding and its associated loss of platelets
and clotting factors.2,3,7,11 Whether or not pharmacological
lowering of blood pressure is beneficial remains to be
conclusively shown.3,7
Treatment Site
EVAR procedures are optimally performed at a site
that is equipped for excellent fluoroscopic imaging and open surgery because some patients will require OR or
open adjuncts to their EVAR, such as an iliac conduit,
femorofemoral bypass, or laparotomy for relief of
abdominal compartment syndrome.
Anesthesia and Catheter-Guided Placement
The latter should be achieved percutaneously under
local anesthesia. This permits arteriography to define
aortic and arterial anatomy, facilitates large sheath and
supraceliac balloon placement if needed, and prevents
circulatory collapse caused by the induction of general
anesthesia. Whether general anesthesia is used later to
eliminate motion and improve fluoroscopic imaging to
permit precise graft deployment remains controversial.
One group has successfully used local anesthesia supplemented
by sedation throughout as an alternative.1,3,7
Supraceliac Aortic Sheath Placement
and Balloon Control
Most experienced groups favor this approach only
when there is severe circulatory collapse. In such cases,
deflation of the balloon before sealing the rupture site
will result in immediate recurrence of the circulatory collapse.
Therefore, techniques have been developed to
maintain continuous aortic control until the endograft
has sealed the leak.2,3,7,12,13 These techniques use multiple
balloons to minimize renal and visceral ischemia by placing
secondary balloons within the endograft while the
supraceliac balloon is deflated and removed through its
supporting sheath.
Endograft Type and Configuration
Both bifurcated and aorto-uni-iliac (or femoral) grafts
can be used successfully, although some patients have
unilateral iliac disease, which mandates a unilateral configuration.
Modular and unibody grafts have been used successfully
in both configurations. An appropriate inventory
of suitable grafts and accessories must be stocked
sterile in the treatment site and be available for the procedure
and unexpected contingencies.
Abdominal Compartment Syndrome
Abdominal compartment syndrome is a major cause of
morbidity and mortality after EVAR for rAAA. It is advantageous
to keep a high index of suspicion for this entity.
Laparotomy and hematoma evacuation have alleviated the hypotension, high ventilatory compliance, and oliguria
that occurs with the full-blown syndrome. Monitoring
bladder pressure has been helpful in the early detection of
the syndrome,3,7 and early laparotomy with open
abdomen treatment and suction/sponge dressings may
decrease mortality and allow survival in otherwise hopeless
circumstances when small bowel and mesenteric
edema cause loss of domain for the abdominal viscera.7,14
EVAR for the Highest-Risk Patients
It is probable that EVAR is most beneficial in augmenting
survival when it is used in the highest-risk
patients who are unlikely to survive an OR. Patients
with hemodynamic instability and profound circulatory
collapse, a hostile abdomen, or those unable to receive
transfusion would fall into this category. If such
patients, particularly those who are hemodynamically
unstable, are excluded from EVAR, it is likely that the
improved survival that can accrue from this form of
treatment will be diminished.8
DISCUSSION
It is clear that several centers in which the physicians and surgeons are enthusiastic about EVAR treatment for rAAAs attempted to perform the procedure preferentially in every AAA patient with suitable anatomy.8 This includes patients who are hypotensive and hemodynamically unstable, as well as those with frank hemorrhagic shock. These centers have achieved favorable results with EVAR for rAAAs in these unstable patients and believe that it is precisely these high-risk, unstable, hypotensive patients in whom EVAR offers the greatest survival benefit over OR. In these centers, between 28% and 79% (mean, 49.1%) of all rAAA patients were treated by EVAR. In addition, the proportion of patients treated by EVAR increased with time as devices and skills improved and enthusiasm for the procedure increased, and it is likely that the proportion will increase further as new devices and techniques are introduced. All of these centers that are enthusiastic about EVAR treatment of rAAAs emphasize several key factors that are important in achieving favorable outcomes in these patients. Proper use of aortic balloon control, adequate recognition and treatment of abdominal compartment syndrome, and the establishment of a structured system and protocol for the treatment of rAAA patients all contribute to improved survival outcomes in patients with this diagnosis.
CONCLUSION
Although there may be other ways to deal with these and other factors and still achieve good outcomes with EVAR in the rAAA setting, the strategies, techniques, and adjuncts outlined in this article are one way of doing so that has proven to be effective.
Frank J. Veith, MD, is Professor of Surgery at New York University Medical Center in New York, and Professor of Surgery at the Cleveland Clinic in Cleveland, Ohio. He has disclosed that he holds no financial interest in any product or manufacturer mentioned herein. Dr. Veith may be reached at (718) 549-3140; fjvmd@msn.com.
Neal S. Cayne, MD, is Associate Professor of Surgery at New York University Medical Center in New York. He has disclosed that he holds no financial interest in any product or manufacturer mentioned herein.
Todd L. Berland, MD, is Assistant Professor of Surgery at New York University Medical Center in New York. He has disclosed that he holds no financial interest in any product or manufacturer mentioned herein.
Dieter Mayer, MD, is Associate Professor of Surgery at Zurich University Hospital in Zurich, Switzerland. He has disclosed that he holds no financial interest in any product or manufacturer mentioned herein.
Mario Lachat, MD, is Professor of Surgery at Zurich University Hospital in Zurich, Switzerland. He has disclosed that he holds no financial interest in any product or manufacturer mentioned herein.
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